Fuel Injection Valve

ABSTRACT

In a fuel injection valve used for an internal combustion engine, a valve closing lag time due to fluid resistance in a fuel path is shortened to decrease a minimum injection limit. More specifically, in the fuel injection valve in which an anchor is attracted to an end face part of a stationary core having a fuel path formed at a center part thereof by means of electromagnetic force, and in which a fuel injection hole is opened and closed by controlling a valve disc driven in conjunction with the anchor, there are provided a fuel reservoir part at a center part of an upper end face part of the anchor, a through hole extending axially in a fashion that an end part thereof is open to the fuel reservoir part, and a fuel path extending radially outward from the fuel reservoir part so that fuel is fed to a magnetic attraction gap between an upper end face part of the anchor and a lower end face part of the stationary core. Further, an opening part of a through hole that is open to an upper end face part of the anchor is at least partially opposed to a fuel introduction bore formed in the stationary core, and on the opening part of the through hole, a fuel introduction part is provided for capturing fuel running radially outward from a center side part of the anchor and for guiding the fuel thus captured to the through hole.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel injection valve used in aninternal combustion engine, and more particularly to a fuel injectionvalve that opens and closes a fuel path by an electromagnetically drivenmovable member thereof.

2. Description of the Related Art

A conventional type of fuel injection valve is disclosed in JapaneseUnexamined Patent Publication No. H11 (1999)-22585, which describes atechnique for improving valve behavior responsivity through reduction offluid resistance in movement of an anchor by providing a vertical grooveon the periphery of the anchor.

In Japanese Unexamined Patent Publications No. S58 (1983)-1778863 andNo. H18 (2006)-22721, there is disclosed a movable member comprising acylindrical anchor part, a plunger part located at the center part ofthe anchor part, and a valve disc mounted at the top end of the plungerpart, wherein a magnetic attraction gap is provided between an end faceof the anchor part and an end face of a stationary core having a fuelintroduction bore for introducing fuel centerward, and wherein anelectromagnetic coil is provided for applying a magnetic flux to amagnetic path including the magnetic attraction gap. A technique forforming an axially extending through hole in the anchor part is alsodescribed in the patent publications noted above.

Japanese Unexamined Patent Publication No. H14 (2002)-528672 discloses astructure in which a plunger is disposed through the center of an anchorpart, and an axially extending through hole that penetrates the anchorpart is provided in the periphery portion of the anchor part.

SUMMARY OF THE INVENTION

In the conventional techniques described above, fluid resistance in afuel path disposed in an anchor has an adverse effect on movement of theanchor, resulting in unsatisfactory improvement in responsivity at thetime of valve opening or closing.

It is therefore an object of the present invention to increase aresponse speed of valve opening and closing in a fuel injection valve byenabling sufficiently smooth movement of a movable member including ananchor so that fuel fed from a fuel introduction bore of a stationarycore to the anchor can smoothly run to the downstream side of the anchoror so that, under particular conditions, fuel can smoothly move from thedownstream side of the anchor to the upstream side thereof.

In accomplishing this object of the present invention and according toone aspect thereof, there is provided a fuel injection valve in which anopening part of a through hole that is open to the upper end face of ananchor is disposed at a position that is at least partially opposed to afuel introduction bore of a stationary core, and a fuel introductionpart is provided at the opening part of the through hole so that fuelflowing outward from the center side of the anchor is captured andguided to the through hole.

The length of the through hole is preferably shorter than the axialdimension of the anchor, and at the upper end part (stationary coreside) of the through hole, the fuel introduction part is preferablyformed so as to be open centerward in addition to the provision of theopening part opposed to the stationary core.

A fuel injection valve structured as mentioned above in accordance withthe present invention can provide enhanced responsivity of valve openingand closing.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an entire structural arrangement of afuel injection valve in a preferred embodiment of the present invention;

FIG. 2 is an enlarged fragmentary sectional view showing a part of FIG.1;

FIG. 3 presents a plan view showing an anchor in a preferred embodimentof the present invention and a sectional view showing the center part ofthe anchor;

FIG. 4 is a sectional view showing flows of fuel at the time of closingan injection hole;

FIG. 5 is a graph showing the characteristics of magnetic attraction ofthe anchor;

FIG. 6 is a plan view showing an anchor in another preferred embodimentof the present invention;

FIG. 7 is a plan view of an anchor in another preferred embodiment ofthe present invention;

FIG. 8 is a plan view showing an anchor in another embodiment of thepresent invention; and

FIG. 9 is an enlarged fragmentary sectional view showing a part of afuel injection valve in another preferred embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail by way of examplewith reference to the accompanying drawings. Referring first to FIGS. 1and 2, there is shown an entire structural view of a first preferredembodiment of the present invention to be described below.

FIG. 1 is a longitudinal cross-section view of a fuel injection valve inthe first preferred embodiment, and FIG. 2 is an enlarged view of a partof FIG. 1, showing details of the fuel injection valve in the firstpreferred embodiment.

A nozzle pipe 101 made of metal comprises a small-diameter cylindricalpart 22 having a relatively small diameter and a large-diametercylindrical part 23 having a relatively large diameter, both thecylindrical parts 22 and 23 being joined with ether other via a conicalsection part 24.

A nozzle tip is formed at an end of the small-diameter cylindrical part22. More specifically, on an internal cylindrical region formed at theend of the small-diameter cylindrical part 22, a guide member 115 havinga guide bore for guiding fuel centerward and an orifice plate 116 havinga fuel injection hole 116A are stacked and inserted in that order, andthe periphery of the orifice plate 116 is secured to the internalcylindrical region by welding.

The guide member 115 serves to guide movement of a plunger 114A of amovable member 114 to be described later, i.e., movement of a valve disc114B provided at an end of the plunger 114A, and the guide member 115also serves to guide fuel inward from the radially outer side of thevalve disc 114B.

The orifice plate 116 has a conical valve seat 39 formed at a positionfacing the guide member 115. The valve disc 114B provided at the end ofthe plunger 114A is moved to abut the valve seat 39 or to come off thevalve seat 39 so that a flow of fuel is cut off from the fuel injectionhole 116A or injected therethrough.

On the periphery of the nozzle tip, there is formed a groove in which atip seal made of resin or a seal member represented by a gasket havingrubber material plated on a metal part thereof is press-fitted.

At the lower end of the inner circumference of the large-diametercylindrical part 23 of the metallic nozzle pipe 101, a plunger guide 113for guiding the plunger 114A of the movable member 114 is securelypress-fitted with a drawn part 25 of the large-diameter cylindrical part23.

At the center of the plunger guide 113, a guide bore 127 is provided forguiding the plunger 114A, and a plurality of fuel paths 126 are formedaround the guide bore 127.

Further, on the upper side of the center of the plunger guide 113, arecessed part 125 is formed by extrusion processing. A spring 112 isheld in the recessed part 125.

On the lower side of the center of the plunger guide 113, a protrudedpart corresponding to the recessed part 125 is formed by extrusionprocessing so that the guide bore 127 for the plunger 114A is providedat the center of the protruded part.

Thus, the plunger 114A, which has an elongated shape, is guided by theguide bore 127 of the plunger guide 113 and the guide bore of the guidemember 115 to perform straight reciprocating motion.

Since the metallic nozzle pipe 101 is formed as an integral memberincluding the top end portion and back end portion thereof in thearrangement mentioned above, the nozzle pipe 101 is easy to manage as acomponent part and advantageous in workability at the time of assemblingat a workshop.

At the opposite end of the plunger 114A from the end thereof having thevalve disc 114B, there is provided a head part 114C comprising steppedparts 129 and 133 that have an outside diameter larger than the diameterof the plunger 114A. A seat face for a spring 110 is provided on theupper end face of the stepped part 129, and a protrusion 131 used as aspring guide is formed at the center thereof.

The movable member 114 comprises an anchor 102 which has, at the centerthereof, a plunger through hole 128 for penetration of the plunger 114A.

On the anchor 102, a recessed part 112A is formed as a spring bracketseat at the center of the face opposed to the plunger guide 113, and thespring 112 is held between the recessed part 112A and the recessed part125 of the plunger guide 113.

Since the plunger through hole 128 has a diameter smaller than thediameters of the stepped parts 133 and 129 formed on the head part 114C,the lower end face of the inner circumference of the stepped part 129formed on the head part 114C of the plunger 114A abuts a bottom face123A of a recessed part 123 formed on the upper side face of the anchor102 held by the spring 112 under the action of a biasing force of thespring 110 that pushes the plunger 114A toward the valve seat of theorifice plate 116 or under the action thereof in combination with theinfluence of gravity, thereby bringing about engagement between theplunger 114A and the anchor 102.

Thus, both the plunger 114A and anchor 102 are operatively associated tomove together in upward movement of the anchor 102 against the biasingforce of the spring 112 or the force of gravity, or in downward movementof the plunger 114A along the biasing force of the spring 112 or theforce of gravity.

In contrast, when a force of moving the plunger 114A upward is appliedthereto independently or when a force of moving the anchor 102 downwardis applied thereto independently, the plunger 114A and the anchor 102are to be moved in directions opposite to each other regardless of thebiasing force of the spring 112 or the force of gravity.

In this step of operation, a film of fluid existing in a micro gap of 5to 15 micrometers between the outer circumferential face of the plunger114A and the inner circumferential face of the anchor 102 at thelocation of the plunger through hole 128 produces friction against theopposite-direction movements of the plunger 114A and the anchor 102,causing suppression of the movements thereof. That is to say, a brakingforce is applied to rapid displacements of the plunger 114A and theanchor 102. There occurs little frictional resistance in slow movementsof the plunger 114A and the anchor 102, and therefore, momentaryopposite-direction movements of the plunger 114A and the anchor 102attenuate in a short time.

In the state mentioned above, the center position of the anchor 102 isheld by the inner circumferential face of the plunger through hole 128of the anchor 102 and the outer circumferential face of the plunger114A, not by the inner circumferential face of the large-diametercylindrical part 23 and the outer circumferential face of the anchor102. The outer circumferential face of the plunger 114A serves as aguide for the anchor 102 in independent axial movement thereof.

Although the lower end face of the anchor 102 is opposed to the upperend face of the plunger guide 113, there occurs no direct contactbetween the lower end face of the anchor 102 and the upper end face ofthe plunger guide 113 because of the intervention of the spring 112.

A side gap 130 is provided between the outer circumferential face of theanchor 102 and the inner circumferential face of the large-diametercylindrical part 23 of the metallic nozzle pipe 101. For allowing axialmovement of the anchor 102, the side gap 130 is so arranged as toprovide a clearance dimension of approximately 0.1 millimeter forexample, which is larger than the micro gap of 5 to 15 micrometersbetween the outer circumferential face of the plunger 114A and the innercircumferential face of the anchor 102 at the location of the plungerthrough hole 128. Since an increase in the size of the side gap 130tends to increase magnetic resistance, the size of the side gap 130 isto be determined in consideration of an effect of magnetic resistance.

A stationary core 107 is press-fitted on the inner circumferential faceof the large-diameter cylindrical part 23 of the metallic nozzle pipe101, and a fuel introduction pipe 108 is press-fitted on the upper endface of the stationary core 107. Weld-jointing is made at a press-fittedposition between the large-diameter cylindrical part 23 of the nozzlepipe 101 and the fuel introduction pipe 108 so as to hermetically seal afuel leakage clearance to be formed between the inside of thelarge-diameter cylindrical part 23 of the metallic nozzle pipe 101 andoutside air.

Along the center line of the fuel introduction pipe 108 and thestationary core 107, there is provided a through hole 107D having adiameter D that is slightly larger than the diameter of the head part114C of the plunger 114A.

At the lower end of the inner circumference of the through hole 107Dused as a fuel introduction path in the stationary core 107, the headpart 114C of the plunger 114A is inserted in a non-contact state, andbetween a lower end edge 132 of the inner circumference of the throughhole 107D in the stationary core 107 and an outer circumferential edge132 of the stepped part 133 of the head part 114C, there is provided agap S1 having almost the same size as that of the side gap 130 mentionedabove. In this arrangement, a clearance dimension larger than a gap ofapproximately 40 to 100 micrometers on an inner circumferential edge 135of the anchor 102 is provided in order to minimize magnetic flux leakagefrom the stationary core 107 to the plunger 114A.

For initial load setting, the lower end of the spring 110 abuts a springbracket seat 117 formed on the upper end face of the stepped part 133provided on the head part 114C of the plunger 114A, and the other end ofthe spring 110 is placed on an adjuster 54 press-fitted in the inside ofthe through hole 107D of the stationary core 107 so that the spring 110is held between the head part 114C and the adjuster 54.

By adjusting a setting position of the adjuster 54, it is possible toadjust an initial load to be applied when the spring 110 pushes theplunger 114A against the valve seat 39.

At the time of stroke adjustment of the anchor 102, an electromagneticcoil (104, 105) and a yoke (103, 106) are attached to the periphery ofthe large-diameter cylindrical part 23 of the nozzle pipe 101, and thenthe anchor 102 is set in the inside of the large-diameter cylindricalpart 23 of the nozzle pipe 101. With the plunger 114A inserted throughthe anchor 102, the plunger 114A is pressed to a valve closing positionby using a jig, and a position of press-fitting the stationary core 107is determined while a stroke of the movable member 114 is checked whenthe electromagnetic coil 105 is energized. In this manner, the strokingof the movable member 114 can be adjusted to an arbitrary position.

As shown in FIGS. 1 and 2, with an initial load of the spring 110adjusted in initial load setting, the lower end face of the stationarycore 107 is opposed to an upper end face 122 of the anchor 102 of themovable member 114 via a magnetic attraction gap 136 of approximately 40to 100 micrometers (slightly exaggerated for purposes of illustration).In comparison between the outside diameter of the anchor 102 and theoutside diameter of the stationary core 107, the outside diameter of theanchor 102 is slightly (approximately 0.1 millimeter) smaller than thatof the stationary core 107. By way of contrast, the inside diameter ofthe plunger through hole 128 formed at the center of the anchor 102 isslightly larger than the diameters of the plunger 114A and valve disc114B of the movable member 114. The inside diameter of the through hole107D formed in the stationary core 107 is slightly larger than theoutside diameter of the head part 114C, which is larger than the insidediameter of the plunger through hole 128 of the anchor 102.

In the structure mentioned above, while an adequate area of magneticpassage is provided in the magnetic attraction gap 136, an allowance foraxial engagement is provided between the lower end face of the head part114C of the plunger 114A and the bottom face 123A of the recessed part123 of the anchor 102.

On the periphery of the large-diameter cylindrical part 23 of themetallic nozzle pipe 101, a cup-shaped yoke 103 having an open-sidemouth is provided, and a toroidal upper yoke 106 is secured so as tocover the open-side mouth of the cup-shaped yoke 103.

At the center of the bottom part of the cup-shaped yoke 103, a throughhole is provided, and the large-diameter cylindrical part 23 of themetallic nozzle pipe 101 is inserted through the through hole. On anouter circumferential wall part of the cup-shaped yoke 103, an outercircumferential yoke part is formed which is opposed to the outercircumferential face of the large-diameter cylindrical part 23 of themetallic nozzle pipe 101. The outer circumferential face of the toroidalupper yoke 106 is press-fitted with the inner circumferential face ofthe cup-shaped yoke 103.

In a cylindrical space formed by the cup-shaped yoke 103 and thetoroidal upper yoke 106, there is disposed a toroidal or cylindricalelectromagnetic coil 105.

The electromagnetic coil 105 comprises a toroidal coil bobbin 104 havinga U-shaped groove that is open radially outward, and a toroidal coilelement 105 formed of a copper wire wound in the U-shaped groove.

The bobbin 104, coil element 105, cup-shaped yoke 103, and upper yoke106 are included in an electromagnetic coil device arrangement.

A rigid conductor 109 is secured to each of the beginning of the coilelement 105 and the end thereof, and the conductor 109 is led out via athrough hole formed in the upper yoke 106. The peripheries of theconductor 109, the fuel introduction pipe 108, and the large-diametercylindrical part 23 of the nozzle pipe 101 are molded in a process inwhich insulating resin is injected into the upper part of the upper yoke106 on the inner circumference of an opening on the upper end of thecup-shaped yoke 103. Thus, the peripheries of the conductor 109, thefuel introduction pipe 108, and the large-diameter cylindrical part 23of the nozzle pipe 101 are covered with resin mold 121. In this manner,a toroidal magnetic path 140 indicated by the arrow 140 in FIG. 2 isformed around the electromagnetic coil (104, 105).

A plug for supplying electric power from a battery power supply isconnected to a connector 43A formed at the top end part of a conductor43C, and a sequence of energization and non-energization is controlledby a controller (not shown).

When the coil 105 is energized, a force of magnetic attraction isproduced in the magnetic attraction gap 136 between the anchor 102 ofthe movable member 114 and the stationary core 107 by a magnetic fluxpassing through the magnetic path 140, causing the anchor 102 to moveupward since the attractive force thus produced exceeds a preset load ofthe spring 110. In this step of operation, the anchor engages the headpart 114C of the plunger 114A, and moves upward in conjunction with theplunger 114A until the upper end face of the anchor 102 abuts the lowerend face of the stationary core 107. Accordingly, the valve disc 114B atthe top end of the plunger 114A comes off the valve seat 39, so thatfuel is run through a fuel path 118 and injected into a combustionchamber via a plurality of the fuel injection holes 116A.

When the electromagnetic coil 105 is de-energized, the magnetic fluxpassing through the magnetic path 140 disappears to remove the force ofmagnetic attraction from the magnetic attraction gap 136.

In this state, a biasing force of the spring 110 for initial loadsetting, which pushes the head part 114C of the plunger 114A in theopposite direction, overcomes a biasing force of the spring 112, actingon the movable member 114 entirely (anchor 102, plunger 114A).Resultantly, the anchor 102 of the movable member 114, from which theforce of magnetic attraction has been removed, is returned to the valveclosing position where the valve disc 114B comes into contact with thevalve seat 39.

In this step of operation, the stepped part 129 of the head part 114Cabuts the bottom face 123A of the recessed part 123 of the anchor 102,causing the anchor 102 to be moved toward the plunger guide 113 with aforce overcoming the biasing force of the spring 112.

When the valve disc 114B strikes the valve seat 39 vigorously, theplunger 114A bounces off in a direction of compressing the spring 110.However, since the anchor 102 is provided as a component independent ofthe plunger 114A, the plunger 114A leaves the anchor 102 to move in theopposite direction from the movement of the anchor 102.

Under this condition, friction is produced on a fluid between the outercircumferential face of the plunger 114A and the inner circumferentialface of the anchor 102, so that the kinetic energy of bouncing-off ofthe plunger 114A is absorbed by an inertial mass of the anchor 102 whichis still in movement to the opposite direction (valve closing direction)due to an inertial force of the anchor 102.

At the time of bouncing-off of the plunger 114A, since the anchor 102having a relatively large inertial mass separates from the plunger 114A,the energy of bouncing-off itself decreases. Further, when the anchor102 absorbs the energy of bouncing-off of the plunger 114A, the inertialforce of the anchor 102 decreases accordingly to reduce the energy ofcompressing the spring 112, causing a decrease in repulsive force of thespring 112. Thus, there hardly occurs a phenomenon of movement of theplunger 114A in the valve opening direction due to the bouncing-off ofthe anchor 102 itself.

In the manner mentioned above, the bouncing-off of the plunger 114A isminimized, i.e., a phenomenon of so-called secondary injection issuppressed in which fuel is injected randomly by valve openingimmediately after de-energization of the electromagnetic coil (104,105).

In the design of a fuel injection valve, it is required that the fuelinjection valve be able to perform valve opening and closing actions inquick response to an input valve opening signal. More specifically, alag time from the rise of a valve opening pulse signal until theaccomplishment of an actual open valve state (valve opening lag time)and a lag time from the fall of the valve opening pulse signal untilaccomplishment of an actual closed valve state (valve closing lag time)should be shortened, which is also of key importance from the viewpointthat a minimum controllable fuel injection quantity (minimum injectionlimit) should be decreased. It is commonly known that the shortening ofa valve closing lag time is effective in decreasing the minimuminjection limit.

As a technique for shortening a valve closing lag time, it isconceivable to increase a preset load of the spring 110 to be applied tothe movable member 114 as a force for transition from an open state ofthe valve disc 114B to a closed state thereof. However, an increase inthis force results in the need for increasing a valve opening force,giving rise to the disadvantageous problem that a larger-sizedelectromagnetic coil must be used. Because of a limitation imposed onstructural design of a fuel injection valve, the technique stated abovecan achieve only a limited success in shortening a valve opening lagtime.

As another technique for shortening a valve closing lag time, anarrangement based on the following principle of operation can beproposed: When the anchor 102 attracted by a force of electromagneticattraction of the stationary core 107 is pushed downward by the spring110, the magnetic attraction gap 136 between the lower end face of thestationary core 107 and the upper end face 122 of the anchor 102 is putin a negative pressure state. By utilizing this phenomenon, fuelthrusted aside by movement of the anchor 102 is made to flow quicklyinto the magnetic attraction gap 136 from the fuel path 118.

Described below is a preferred embodiment of the present invention basedon the above-mentioned principle of operation. In the present preferredembodiment, for shortening a valve closing lag time, a through hole forfuel passage 124 (150 to 153) is provided in the anchor 102 so that fuelflows in the axial direction thereof, an opening part of the throughhole open to the upper end face of the anchor 102 is disposed at aposition that is at least partially opposed to the fuel introductionbore 107D of the stationary core 107, and a fuel introduction part isprovided at the opening part of the through hole so that fuel flowingoutward from the center side of the anchor 102 is captured and guided tothe through hole.

The length of the through hole is preferably shorter than the axialdimension of the anchor 102, and at the upper end (stationary core side)of the through hole, the fuel introduction part is preferably formed soas to be open centerward in addition to the provision of the openingpart opposed to the lower end face of the stationary core 107.

FIG. 3 shows the structure of the anchor 102 in the present preferredembodiment of the invention. FIG. 3(A) is a plan view taken from theplunger head part 114C, and FIG. 3(B) is a sectional view of (A) takenalong the line X-X.

At the center part of the anchor 102, the recessed part 123 is provided,and at the center part of the bottom face 123A thereof, the plungerthrough hole 128 is formed for penetration of the plunger 114A of themovable member 114.

Four vertical grooves 150B to 153B, each having a semicircular crosssection and constituting a part of each of the through holes 150 to 153for fuel passage, are formed at equally spaced intervals on an innercircumferential wall part of the recessed part 123. Located at the upperpositions of the through holes 150 to 153, the vertical grooves 150B to153B serve as a fuel introduction part for capturing fuel flowingoutward from the center side of the anchor 102.

The vertical grooves 150B to 153B run to the bottom face 123A of therecessed part 123, being straight open on the end face opposite to thestationary core side of the anchor 102. Each of the portions extendingfrom the vertical grooves 150B to 153B through the bottom face 123A isformed to provide a circular cross section as a part of each of thethrough holes 150 to 153. As arranged in the fashion mentioned above, onthe bottom face 123A, there are provided through holes 150A to 153A eachhaving a semicircular cross section that projects centerward from theouter circumference of the bottom face 123A. Although each of thethrough holes 150 to 153 having a circular cross section is formed by acombination of each of the through holes 150A to 153A having asemicircular cross section and each of the vertical grooves 150B to 153Bhaving a semicircular cross section in the present preferred embodiment,a diametrical dimension of each of the through holes 150A to 153A havinga semicircular cross section may be larger or smaller than a diametricaldimension of each of the vertical grooves 150B to 153B having asemicircular cross section. There may also be provided such anarrangement that each of the cross sections of the through holes 150A to153B and the vertical grooves 150B to 153B has a rectangular or anyother shape. That is to say, each of the through holes 150 to 153 shouldbe formed in a stepped structure so that at least a part thereof is openon the bottom face of the recessed part 123 of the anchor 102 or open atany midway position recessed from the end face 112 of the anchor 102,and so that the remaining part thereof is open on the end face 112 ofthe anchor 102 or open at a position that is nearer to the end face 122of the anchor 102 than the above-stated open part that is located on thebottom face of the recessed part 123 or at any recessed midway position.In this structural arrangement, fuel is captured by each of the verticalgrooves 150B to 153B serving as an fuel introduction part, and the fuelthus captured is guided to each of the through holes 150A to 153A,thereby ensuring smooth fuel flowing to enhance the responsivity of theanchor 102.

A part of each of the through holes 150 to 153 is formed at an innerposition radially inward from the diameter of the fuel introduction bore107D of the stationary core 107, and the remaining part thereof isformed at an outer position radially outward from the diameter of thefuel introduction bore 107D. In this arrangement, the position ofopening at the upper end of each of the through holes 150 to 153 locatedat the inner position radially inward from the fuel introduction bore107D is disposed at a position that is farther apart from the end faceof the stationary core 107 than the position of opening at the upper endof each of the through holes 150 to 153 located at an outer positionradially outward from the fuel introduction bore 107D.

In the present preferred embodiment structured as described above, fuelrunning from the fuel introduction bore 107D flows into each of thethrough holes 150 to 153, and also the fuel flows over the opening ofeach of the through holes 150 to 153 to run toward the radially outerside of the end face of the anchor 102, thereby enabling quick fuelmovement in the magnetic attraction gap.

In FIG. 3, the solid line 123o indicates the diameter of the recessedpart 123, representing the inner circumferential wall of the recessedpart 123. The broken line 107ø indicates the inside diameter of the fuelintroduction bore 107D of the stationary core 107, and the dot-dash line117Ø indicates the outside diameter of the spring bracket seat 117formed on the head part 114C of the plunger 114A. As shown in FIGS. 3and 2, in introduction of fuel from the lower end of the stationary core107 to the recessed part 123, the fuel is fed via the gap S1 formed as afuel path formed between the edge 132 of the inner circumference of thestationary core 107 and an edge 134 of the outer circumference of theupper end of the spring bracket seat 117. Since the opening of each ofthe through holes 150 to 153 is formed at an immediately downstreamposition of the fuel path (almost directly below the fuel path), smoothfuel flowing can be ensured. Further, fuel running through each of thethrough holes 150 to 153 from the fuel path 118 also flows smoothly intothe magnetic attraction gap 136 in a negative pressure state between theend face 112 of the anchor 102 and the end face of the stationary core107. That is, smooth fuel movement is allowed because of the formationof an almost straight way of fuel passage from the fuel introductionbore 107D to the fuel path 118. Further, as regards the magneticattraction gap 136 between the end face 122 of the anchor 102 and theend face of the stationary core 107, since a part of each of the throughholes 150 to 153 is extended in such a shape that the recessed part 123expands radially outward, fuel from the gap S1 between the edge 132 ofthe inner circumference of the stationary core 107 and the edge 134 ofthe outer circumference of the upper end of the spring bracket seat 117and fuel from the recessed part 123 are fed smoothly into the magneticattraction gap 136 between the end face 122 of the anchor 102 and theend face of the stationary core 107.

In this arrangement, the sum total of the cross-sectional path areas ofthe through holes 150 to 153 is larger than the cross-sectional patharea of the fuel path formed in the gap S1, so that a cross-sectionalarea in the direction of fuel flow is widened to allow smoother flowingof fuel.

Further, since the recessed part 123 is provided as a broadened part offuel passage at a downstream position with respect to thecross-sectional path area of the fuel path formed in the gap S1, fuelrunning through the gap S1 is fed smoothly into the through holes 150 to153 and also into the magnetic attraction gap 136. At this step, theupper end part of each of the grooves 150B to 153B serves to feed fuelsmoothly from the recessed part 123 to the recessed part 122 on theouter circumferential side of the anchor 102 through each of recessedparts 160 to 163.

The depth dimension of the recessed part 123 is to be determinedappropriately according to the height dimension of the head part 114C ofthe plunger 114A.

Although the diameter of the recessed part 123 should be larger than theinside diameter of the stationary core 107, it is necessary to determinean extent of increase in the diameter of the recessed part 123 inconsideration of magnetic characteristics with respect to the stationarycore 107. In an example of embodiment in which the diameter of therecessed part 123 is expanded to the outermost diameter positions of thethrough holes 150 to 153, it has been found that satisfactory magneticcharacteristics can be attained.

Further, there is provided such an arrangement that the sum total of thecross-sectional path areas of the through holes 150 to 153 is largerthan the cross-sectional area of the plunger through hole 128 forpenetration of the plunger 114A.

Thus, the cross-sectional area of fuel passage can be made larger thanthat in the case of provision of a through hole in the plunger.According to the structure demonstrated in the present preferredembodiment, there may also be provided a modification in which a throughhole is formed at the center position of the plunger 114A or at an outercircumferential position thereof so as to widen the cross-sectional areaof fuel passage.

In particular, where the through holes 150 to 153 formed in the anchor102 and the fuel path 126 formed in the plunger guide 113 are alignedcircumferentially and radially at the time of assembling, a straightfuel path can be formed from the fuel introduction bore of thestationary core to the fuel path 118 on the downstream side of theplunger guide 113, thereby making it possible to provide entirely smoothmovement of the movable member 114 including the anchor 102.

FIG. 4 shows a sectional view of the anchor 102 assembled in a fuelinjection valve. The upper end face 122 of the anchor 102 is opposed tothe stationary core 107 via the magnetic attraction gap 136, and thelower end face thereof is opposed to the plunger guide 113 via the fuelpath. Further, on the bottom face 123A of the recessed part 123, thehead part 114C of the movable member 114 is located, and the springbracket seat 117 is located on the upper part thereof (indicated by thebroken line in FIG. 3 (B)).

The following describes flows of fuel at the time of valve closing withreference to FIG. 4.

In a common application of a fuel injection valve used in a gasolineinternal combustion engine of a cylinder direct injection type wherefuel is fed at high pressure, fluid resistance on fuel passage haslittle effect on a valve opening lag time in valve opening operation forfuel injection since fuel is pressed a high pressure.

By way of contrast, when the valve disc 114B closes the fuel injectionhole 116A in valve closing operation for cutting fuel off, a proportionof fuel thrusted against the direction of fuel fed at high pressurecauses a counterflow. It is therefore required that fluid resistance onfuel passage be adequately small.

With reference to FIG. 4, the valve closing operation is described belowusing the through hole 150 of the anchor 102 as a representative portionof fuel passage.

When the valve opening pulse signal falls, a force of magneticattraction is removed from the magnetic path 140, releasing the anchor102 from attraction toward the stationary core 107. Then, the anchor 102is pushed downward by a pushing force of the spring 110, thereby causingthe valve disc 114B to close the injection hole 116A to cut fuel off.

When the valve disc 114B is pushed down to close the injection hole116A, fuel thrusted in reverse 160 reaches the lower end of the anchor102 through the fuel path 126 of the plunger guide 113. Then, the fuelbranches into a flow of fuel 161 going to the side gap 130 of the anchor102 and a flow of fuel going to the through hole 150 of the anchor 102.Since the side gap 130 is as narrow as approximately 0.1 millimeter, thefluid resistance of the side gap 130 is large and the quantity of fuelfed into the magnetic attraction gap 136 through the side gap 130 isextremely small. Therefore, little contribution to improvement in avalve closing lag is expected by rearranging the side gap 130.

Almost all of fuel 202 (162) flowing into the through hole 150A is fedto the vertical groove 150B having a semicircular cross section on theinner circumferential face of the recessed part 123 of the anchor 102since the through hole 150A communicates directly with the verticalgroove 150B.

The vertical groove 150B having a semicircular cross section on theinner circumferential face of the recessed part 123 of the anchor 102 isformed to have direct communication with the through hole 150A in afashion that the vertical groove 150B overlaps with a part of thecircumference of the through hole 150A, i.e., the formation of asemicircular groove corresponding to the diameter of the cross sectionof the through hole 150A is made on the side face of the bottom face123A of the recessed part 123. Hence, on the overlapped part of thethrough hole 150A and the vertical groove 150B having a semicircularcross section on the inner circumferential face of the recessed part 123of the anchor 102, there is no obstacle causing any particular fluidresistance, allowing quick flowing of fuel.

The fuel 202 flowing into the through hole 150A runs to the verticalgroove 150B having a semicircular cross section on the innercircumferential face of the recessed part 123 of the anchor 102 and tothe bottom face 123A of the recessed part 123 of the anchor 102. On theupper part of the bottom face 123A of the recessed part 123, protrusionssuch as the head part 114C of the movable member 114 and the springbracket seat 117 are disposed to cause substantial fluid resistance.Therefore, most of the fuel 202 is fed to the vertical groove 150Bhaving a semicircular cross section on the inner circumferential face ofthe recessed part 123 of the anchor 102.

At the fall of the valve opening pulse signal, the anchor 102 attractedby the force of magnetic attraction of the stationary core 107 is pusheddown by the spring 110, causing a significant decrease in pressure inthe magnetic attraction gap 136 between the lower end face of thestationary core 107 and the upper end face 122 of the anchor 102.

Under the condition mentioned above, the magnetic attraction gap 136 isin a negative pressure state, and the anchor 102 becomes movable whenthe fuel 162 is drawn into the magnetic attraction gap 136. Tofacilitate fuel movement in the magnetic attraction gap 136, it isnecessary to reduce fluid resistance of fuel passage by smoothening theflows of the fuel 160 and fuel 162. That is, the reduction in fluidresistance of fuel passage makes it possible to quicken a valve closingaction.

While the present preferred embodiment has been described with respectto the through hole 150 as a representative portion of fuel passage, itis to be understood that fuel flows through each of the through holes151, 152, and 153 in the same manner.

As aforementioned, in the through hole 150 formed in the anchor 102, thethrough hole 150A directly communicates with the vertical groove 150Bhaving a semicircular cross section on the inner circumferential face ofthe recessed part 123 of the anchor 102, thereby providing anadvantageous effect that the opening area of the through hole issubstantially larger than the dimensional area thereof. Since thecross-sectional area of passage for fuel introduction is made largeradequately, the fluid resistance at the entry of the through hole isreduced to ensure smooth fuel flowing into the through hole. On theother hand, when the anchor 102 moves in the direction of closing theinjection hole 116A, fuel 200 thrusted in the fuel path 118 is quicklymoved to the recessed part 123 via the through holes 150A to 153A, sothat the fuel is quickly fed into the magnetic attraction gap 136 fromthe opening of the upper end having a semicircular cross section,thereby providing an advantageous effect of shortening a valve closinglag time.

In the present preferred embodiment, the outermost part of the throughhole (outside with respect to the axis of the fuel injection valve) isdisposed at an outer position radially outward from the side face of thefuel path formed in the stationary core, and the vertical groove 150Bhaving a semicircular cross section on the inner circumferential face ofthe recessed part 123 of the anchor 102 is disposed to face the magneticattraction gap 136. Thus, smooth fuel feeding into the magneticattraction gap 136 is made easily to reduce fluid resistance. Further,the through hole serves as a primary fuel path in the anchor 102, i.e.,the through hole has a large cross-sectional area for fuel passagethrough the anchor 102. Hence, fuel feeding into the magnetic attractiongap 136 in response to movement of the anchor 102 is made via thethrough hole serving as the primary fuel path. As a result, a voluminalproportion of fuel thrusted at the time of movement of the anchor 102 isfed via the through hole, reducing fluid resistance in fuel passage tothe magnetic attraction gap. A negative pressure occurring in themagnetic attraction gap is therefore decreased to reduce fluidresistance exerted on the anchor 102, thereby bringing out anadvantageous effect of shortening a valve closing lag time.

It is to be noted, however, that such an advantageous effect asmentioned above cannot be obtained merely by providing the anchor 102with the through hole facing the magnetic attraction gap. To ensure anadequate force of magnetic attraction, it is required to decrease themagnetic attraction gap, and in particular, the magnetic attraction gapis extremely small when the anchor 102 is attracted to set up a valveopen state. Therefore, even if the through hole in the anchor has anadequate cross-section area, an aperture for the cross-sectional area ofthe primary flow path is provided as a cylindrical face region formed bythe magnetic attraction gap and the opening edge of the through hole.Since the area of the aperture is extremely small, fuel passage facingthe magnetic attraction gap is made unsatisfactory. To obviate thisproblem in the present invention, there is provided a fuel path on theside of the through hole, the fuel path being arranged to communicatewith the recessed part formed on the anchor 102. In this structuralarrangement, since the recessed part formed on the anchor 102 is incommunication with the fuel path provided on the side of the throughhole, the above-mentioned aperture at the magnetic attraction gap doesnot become a cause of limitation regarding the cross-sectional area ofthe primary flow path.

That is, at a position on the end face of the anchor 102 opposed to thelower end face of the stationary core, there is provided an openingwhich is in communication with the fuel introduction bore of thestationary core and also in communication with the through hole formedin the anchor 102.

More specifically, at the center of the upper end of the anchor 102,there is provided a fuel reservoir part (corresponding to the recessedpart 123, for example) which has a cross-sectional area larger than thatof the fuel introduction bore of the stationary core, and a fuel pathconnected with the fuel reservoir part is formed radially outwardly onthe upper end face of the anchor 102 while the upper end of each of thethrough holes (150A to 153A) formed in the anchor 102 is structured tobe open to the fuel reservoir part.

By the way, the anchor 102 is made of a material having a goodworkability suitable for forging such as magnetic stainless steel or thelike. In fabrication practice wherein the through hole 150 is formed inthe anchor 102 by punching or drilling after the forging of the anchor102, the through hole 150A and the vertical groove 150B having asemicircular cross section on the inner circumferential face of therecessed part 123 of the anchor 102 can be processed at the same timesince the through hole 150A and the vertical groove 150B are to be incommunication with each other, thereby providing an advantageous effectof decreasing the number of processing steps. It is preferred that thevertical groove 150B having a semicircular cross section on the innercircumferential face of the recessed part 123 of the anchor 102 beformed to be larger than the through hole 150A. When the through hole150A is formed by punching after the vertical groove 150B having asemicircular cross section on the inner circumferential face of therecessed part 123 of the anchor 102 is formed by forging, a clearancecan be provided between a punching tool and the vertical groove 150Bhaving a semicircular cross section on the inner circumferential face ofthe recessed part 123 of the anchor 102, which will contribute to easierfabrication of the anchor 102.

Further, the through hole 150 may be formed in the process of forging bysetting a pin at the position thereof.

Although four through holes are disposed at equally spaced intervals inthe anchor 102 shown in FIG. 3, the number of through holes and thecross-sectional area of each of the through holes are to be determinedin consideration of the following relational conditions:

When a current is applied to the electromagnetic coil (104, 105), theanchor 102 is attracted toward the stationary core 107 to move themovable member 114 upward. In the case that the electromagnetic coil(104, 105) and the stationary core 107 are made to meet consistentcharacteristic specifications, a force of magnetic attraction increaseswith an increase in the area of the upper end face 122 of the anchor102, i.e., by increasing the area of the upper end face 122 of theanchor 102, the amount of current to be applied to the electromagneticcoil (104, 105) for obtaining the same level of magnetic attraction canbe reduced to realize electric power saving. Under the condition thatthe same level of current is applied to the electromagnetic coil (104,105), the stationary core 107 and the anchor 102 can be made smaller byincreasing the area of the upper end face 122 of the anchor 102, therebyenabling reduction in the size of the fuel injection valve.

In contrast, as for flows of fuel, fluid resistance decreases as thenumber of through holes is increased and as the cross-sectional area ofeach through hole is increased, and a decrease in fluid resistance has asignificant effect on shortening a valve opening lag time.

Thus, the number of through holes in the anchor 102 and thecross-sectional area of each of the through holes have an influence onthe area of the upper end face 122 in terms of changes in magneticattraction force and valve opening lag time. Since there is a trade-offin the correlation noted above, it is required to carry out designingpractice so as to provide the most advantageous effect.

With reference to FIG. 5, there is shown a graph of experimental resultsof measurements conducted by the inventors, indicating a ratio of thesum total of magnetic path areas of the through holes 150A, 152A, and153A to the magnetic path area (magnetic attraction force) of the upperend face 122 of the anchor 102.

In comparison between a characteristic 170 of a fuel injection valvedesigned according to the present invention and a characteristic 171 ofa conventional fuel injection valve, an improvement is found in themagnetic path (magnetic attraction force) in the fuel injection valveaccording to the present invention.

A magnetic area (magnetic attraction force) required for thecharacteristic 170 corresponds to a range of the characteristic 170 indesign, and it has been verified that the ratio of the sum total ofmagnetic path areas of the through holes to the magnetic path area ofthe anchor 102 is 5% to 15%.

FIG. 6 shows another structure of fuel paths in communication with eachother in the anchor 102 according to another preferred embodiment of thepresent invention.

In the structural arrangement of the through hole 150 for fuel flowingthrough the anchor 150 shown in FIG. 3, the through hole 150A on thedownstream side viewed from the recessed part 123 where the lower endface of the plunger head part 114C is disposed has the same diametricaldimension of that of the vertical groove 150B having a semicircularcross section on the inner circumferential face of the recessed part 123on the upstream side in the anchor. By way of contrast, in thestructural arrangement of the through hole 150 shown in FIG. 6, thevertical groove 150B having a semicircular cross section on the innercircumferential face of the recessed part 123 on the upstream side inthe anchor has a diametrical dimension smaller than that of the throughhole 150A on the downstream side for provision of path communication.

Conversely, with respect to the structural arrangement shown in FIG. 6,the through hole 150A on the downstream side may have a diametricaldimension smaller than that of the vertical groove 150B having asemicircular cross section on the inner circumferential face of therecessed part 123 on the upstream side in the anchor for provision ofpath communication.

While the center lines of the two fuel paths in the anchor 102 shown inFIGS. 3 and 6 are aligned, there may also be provided a modifiedarrangement in which the center lines of the two fuel paths are disposedto deviate from each other for provision of path communication.

As mentioned above, a structural arrangement for communicating flowpaths is to be determined in consideration of a trade-off between themagnetic path area of the upper end face 122 of the anchor to besubjected to magnetic attraction and the degree of lag in valve closingoperation along with the workability of material of the anchor 102.

Further, while the preferred embodiments of the present invention havebeen described as related to the arrangement in which each of thethrough holes 150A, 151A, 152A, and 153A of the through hole 150 on thedownstream side viewed from the bottom face 123A of the recessed part123 is formed in a cylindrical shape, and each of the vertical grooves150B, 151B, 152B, and 153B having a semicircular cross section on theinner circumferential face of the recessed part 123 on the upstream sidein the anchor is formed by providing a circular-arc shape on the sideface of the bottom face 123A of the recessed part 123, it is to beunderstood that the configurations of the through holes 150A to 153A andthe vertical grooves 150B to 153B are not limited to cylindrical andcircular-arc shapes, i.e., the cross sections thereof may be rectangularor elliptic.

The functional features and advantageous effects described hereinabovemake it possible to enhance the responsivity of the fuel injectionvalve, and more particularly to shorten a valve closing lag timethereof. It follows therefore that a minimum injection limitcontrollable by the fuel injection valve can be decreased, e.g., when anengine is in idling, a fuel injection quantity thereof can be decreasedto reduce fuel consumption. Further, even in cases where fuel isinjected a plurality of times per engine stroke, it is allowed to dividea necessary fuel injection quantity into small proportions of fuelinjection.

FIG. 7 shows a structural arrangement of the anchor 102 in anotherpreferred embodiment of the present invention.

In the structural arrangement of the anchor 102 shown in FIG. 7, each ofthe through holes 150A, 151A, 152A, and 153A on the counterflow upstreamside with respect to the bottom face 123A of the recessed part 123 wherethe lower end face of the plunger head part 114C is disposed and each ofthe vertical grooves 150B, 151B, 152B, and 153B having a semicircularcross section on the inner circumferential face of the recessed part 123on the counterflow downstream side in the anchor are formed at differentpositions without being in communication with each other.

Fuel running out of each of the through holes 150A, 151A, 152A, and 153Ais fed to the periphery of the bottom face 123A of the recessed part 123in the anchor and then drawn into the magnetic attraction gap 136through each of the vertical grooves 150B, 151B, 152B, and 153B having asemicircular cross section on the inner circumferential face of therecessed part 123 in the anchor.

In the present preferred embodiment, fuel is fed along the side face ofthe spring bracket seat 117 of the movable member 114 and also fedthrough each of the vertical grooves 150B, 151B, 152B, and 153B having asemicircular cross section on the inner circumferential face of therecessed part 123 in the anchor, thereby bringing about an advantageouseffect of shortening a valve closing lag time.

The preferred embodiments of the invention described so far are digestedbelow:

In the design of an internal combustion engine using a fuel injectionvalve, it is desired to decrease a controllable minimum injection limitin fuel injection quantity since an excessive quantity of fuel injectionin such a state as engine idling is a cause of worsening fuel economy.Further, in an internal combustion engine of a cylinder direct injectiontype, an improved formation of an air-fuel mixture can be made byinjecting fuel a plurality of times per engine stroke, thereby reducingfuel consumption and exhaust emission of HC and NOx. To realizerepetitive actions of fuel injection per stroke in a constant totalquantity of fuel injection, it is required to inject fuel on the basisof measurement of a smaller volume of injection.

For forming a fuel injection valve having a small value of measurableand controllable fuel injection quantity (minimum injection limit),valve opening and closing actions of the fuel injection valve should beperformed at a higher speed. In a technique for implementinghigher-speed actions of valve opening and closing in an electromagnetictype of fuel injection valve, there is provided an arrangement in whichthe electromagnetic responsivity of the valve is made faster and also anintense force of magnetic attraction is produced while a preset load ofa biasing spring is increased so as to apply a larger biasing force atthe time of valve closing.

In another technique for accomplishing the above-mentioned purpose,there is provided an arrangement in which movement of fuel flowing intoa gap S1 between a stationary core and an anchor exerting a force ofvalve opening and closing is smoothened to reduce fluid resistance tothe anchor, thereby suppressing an obstructive force applied to valveactions.

According to a conventional technique for an electromagnetic type offuel injection valve, a vertical groove is provided on a side face of ananchor or on a sliding guide face for the anchor to reduce fluidresistance to the anchor. In the electromagnetic type of fuel injectionvalve, a magnetic passage is formed between the side face of the anchorand the sliding guide face. Therefore, the provision of the verticalgroove on the side face of the anchor or on the sliding guide face isequivalent to the provision of a wide gap across a passage of magneticflux, resulting in a possible decrease in magnetic attraction force. Inparticular, the force of magnetic attraction is likely to decrease incases where the vertical groove is widened with the intention ofimproving the responsivity of valve opening and closing.

Further, according to another conventional technique, there is provideda structure in which a vertical groove is formed as a fuel path forreducing fluid resistance in addition to a primary fuel path formed inan anchor. The primary fuel path formed in the anchor has the largestcross-sectional area than any other fuel paths and therefore providesthe smallest fluid resistance. However, in this structure according tothe conventional technique, the primary fuel path serves only for fluidpassage, not providing a satisfactory function for facilitating fuelmovement into a gap between the anchor and a stationary core. Therefore,there is a disadvantage that the effect of fluid resistance reduction bythe vertical groove having a smaller cross-sectional area than theprimary fuel path is not necessarily adequate on the side of the anchor.

In the fuel injection valve according to the above-mentioned preferredembodiments of the present invention, the toroidal coil is energized toapply a magnetic flux to the magnetic path including the anchor and thestationary core so that a force of magnetic attraction is produced inthe magnetic attraction gap between the end face of the anchor and theend face of the stationary core, thereby attracting the anchor towardthe stationary core. Thus, the valve disc to which the magneticattraction force is transmitted from the anchor is made to come off thevalve seat, thereby opening the fuel path for fuel injection.

In the structure of the fuel injection valve according to theabove-mentioned preferred embodiments of the present invention, thestationary core is secured to the inside of the metallic pipe, theanchor is disposed to be opposed to the stationary core via the magneticattraction gap so that the anchor can reciprocate between a positioncorresponding to the valve seat and a position corresponding thestationary core in the metallic pipe, the toroidal coil is disposed onthe outside of the metallic pipe, the yokes are provided around theupper, lower and circumferential parts of the toroidal coil, the anchorhas a plurality of through holes extending in the axial direction, andthe outer side face of each of the through holes with respect to theaxis of the fuel injection valve is located at an outer positionradially outward from the side face of the fuel path formed at anapproximately center position of the stationary core.

Further, each of the through holes noted above is provided with a fuelfeed path on the stationary core side of the anchor so that fuel can bereceived from the side of the through hole.

In the fuel injection valve according to the above-mentioned embodimentsof the present invention, fluid resistance on fuel passage can bedecreased to allow movement of the anchor at a higher speed, therebymaking it possible to shorten a valve closing lag time.

Referring to FIG. 8, the following describes an another preferredembodiment of the present invention.

In the preferred embodiment shown in FIG. 8, the through holes 150 to153 are formed at equally spaced intervals on the bottom face 123A ofthe recessed part 123 of the anchor 102, and fuel feed grooves 180 to183 are disposed radially from the recessed part 123 on the end face ofthe anchor. At the time of downward movement of the anchor, the fuelfeed grooves 180 to 183 serve to quickly feed fuel from the recessedpart 123 to the magnetic gap 136. The through holes 150 to 153 serve tosmoothly move fuel from the fuel path 118 to the recessed part 123 as inthe foregoing preferred embodiments. According to the present preferredembodiment, there may be provided an arrangement in which the throughholes for promoting fluid flowing in the axial direction and the fuelpaths for guiding fluid in the radial direction are disposed separately.

In addition, a through hole may be formed in the axial direction on thefuel feed grooves 180 to 183.

Further, with reference to FIG. 9, the following describes an anotherpreferred embodiment of the present invention.

In the preferred embodiment shown in FIG. 9, the plunger 114A is securedto the anchor 102 by welding for example, and the anchor 102 and theplunger 114A are thus moved together in any state of operation.

In this structural arrangement, the same advantageous effects as thosein the foregoing preferred embodiments can be attained by providing therecessed part 123 at the center of the anchor 102 and forming thethrough holes and grooves on the bottom face and the innercircumferential face of the recessed part as described with reference toFIG. 2.

It is to be noted that, in FIGS. 1, 2 and 3, reference numeral 101Aindicates a groove formed on the periphery of the metallic pipe 101, anda thin wall part 111 corresponding to the groove 101A constitutes amagnetic aperture in the magnetic passage.

As regards industrial applicability of the present invention, the fuelinjection valve in accordance with the present invention is applicableto injection of any kind of fuel including gasoline, light oil, alcoholor the like used for internal combustion engines.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. A fuel injection valve in which an anchor is attracted to an end facepart of a stationary core having a fuel path formed at a center partthereof by means of electromagnetic force, and in which a fuel injectionhole is opened and closed by controlling a valve disc driven inconjunction with said anchor, said fuel injection valve comprising: athrough hole having an opening part thereof that is open to an upper endface part of said anchor, said opening part being at least partiallyopposed to a fuel introduction bore formed in said stationary core; anda fuel introduction part formed on a said opening part of said throughhole, said fuel introduction part being arranged for capturing fuelrunning radially outward from a center side part of said anchor and forguiding the fuel thus captured to said through hole.
 2. A fuel injectionvalve as claimed in claim 1, wherein the length of said through hole isshorter than the axial dimension of said anchor.
 3. A fuel injectionvalve as claimed in claim 1, wherein said through hole comprises a fuelintroduction part open radially inward to a center side part of saidanchor in addition to said opening part that is open to said upper endface part of said anchor and at least partially opposed to saidstationary core.
 4. A fuel injection valve in which an anchor isattracted to an end face part of a stationary core having a fuel pathformed at a center part thereof by means of electromagnetic force, andin which a fuel injection hole is opened and closed by controlling avalve disc driven in conjunction with said anchor, said fuel injectionvalve comprising: a fuel reservoir part formed at a center part of anupper end face part of said anchor; a through hole extending axially ina fashion that an end part thereof is open to said fuel reservoir part;and a fuel path extending radially outward from said fuel reservoir partso that said fuel path serves to feed fuel to a magnetic attraction gapbetween an upper end face part of said anchor and a lower end face partof said stationary core.
 5. A fuel injection valve in which a magneticflux is applied to a magnetic path including a stationary core and ananchor functioning as a movable component by means of energizing atoroidal coil so that a force of magnetic attraction is produced in amagnetic attraction gap between an end face part of said anchor and anend face part of said stationary core to attract said anchor to saidstationary core, and in which a fuel path is opened by moving a valvedisc mounted at a top end part of said anchor off a valve seat, saidfuel injection valve comprising: an arrangement wherein said anchorcomprises a plurality of through holes for fuel passage extending in theaxial direction of said fuel injection valve; and an arrangement whereinan outermost part of a side face part of each of said plurality ofthrough holes is disposed at an outer position with respect to a sideface part of a fuel path formed in said stationary core.
 6. A fuelinjection valve as claimed in claim 5, wherein, on said anchor, arecessed part is formed at an inner position with respect to anoutermost part of each of said plurality of through holes, and wherein,on an upstream side part with respect to said recessed part, a fuel feedpath is formed for communication between each said through hole and aside face part of said recessed part.
 7. A fuel injection valve asclaimed in claim 5, wherein an outermost part of said fuel feed path forcommunication between each said through hole and said recessed part isformed at an outer position with respect to the inside diameter of saidstationary core.
 8. A fuel injection valve as claimed in claim 5,wherein a side face part of each said through hole has a part thereofthat overlaps with a side face part of said fuel feed path forcommunication between each said through hole and said recessed part. 9.A fuel injection valve as claimed in claim 5, wherein each said throughhole is formed in a cylindrical shape.
 10. A fuel injection valve asclaimed in claim 9, wherein each said through hole is formed in acylindrical shape, said fuel feed path for communication between eachsaid through hole and said recessed part is formed in a circular-arcshape, and the diametrical dimension of the circular arc of said fuelfeed path is slightly larger than each said through hole.
 11. A fuelinjection valve as claimed in claim 5, wherein the sum total of theareas of said plurality of through holes in said anchor is in a range of5% to 15% of the area of a magnetic path in said anchor.
 12. A fuelinjection valve comprising: an anchor having a cylindrical shape; aplunger located at a center part of said anchor; a valve disc disposedat a top end part of said plunger; a stationary core having a fuelintroduction bore for introducing fuel centerward; and anelectromagnetic coil for applying a magnetic flux to a magnetic pathincluding a magnetic attraction gap formed between an end face part ofsaid anchor and an end face part of said stationary core; thearrangement of said fuel injection valve being such that a force ofmagnetic attraction is produced between said end face part of saidanchor and said end face part of said stationary core by said magneticflux that passes through said magnetic gap, said force of magneticattraction being used to attract said anchor to said stationary core fordriving a movable member, whereby said valve disc is moved off a valveseat thereof to open a fuel path provided on said valve seat, whereinsaid anchor of said fuel injection valve comprises: a recessed partformed, on a center part of said anchor, at a position opposed to an endpart of said fuel introduction bore in said stationary core; and aplurality of through holes extending axially through said anchor in afashion that each of said plurality of through holes is open to aperiphery part of said plunger; and wherein a part of a fuel entry ofeach said through hole is open to a bottom face part of said recessedpart, and the remaining part of said fuel entry of said each throughhole is open to an end face part of said anchor.
 13. A fuel injectionvalve as claimed in claim 12, wherein a part of each said through holeis formed on an inner circumferential face part of said recessed part ofsaid anchor, and each said through hole is extended axially in a fashionthat each said through hole penetrates from a bottom part of saidrecessed part to an end face part opposite to the stationary core sideof said anchor.
 14. A fuel injection valve as claimed in claim 12,wherein at least one of said plurality of through holes has a fuel entryon an end face part of said anchor, and the remaining through holes havea fuel entry on a bottom face part of said recessed part.
 15. A fuelinjection valve as claimed in claim 12, wherein a plunger through holefor penetration of said plunger is formed at a center part of saidrecessed part of said anchor, wherein a spring bracket seat for holdingan end of a spring that exerts a biasing force on said plunger formovement thereof toward said valve seat is formed on said plunger,wherein said anchor and said plunger are operatively associated so thatsaid anchor and said plunger are moved axially in conjunction with eachother when said anchor is attracted to said stationary core, and whereinthe sum total of the cross-sectional areas of said plurality of throughholes is larger than the cross-sectional area of said plunger throughhole.
 16. A fuel injection valve as claimed in claim 12, wherein aplunger through hole for penetration of said plunger is formed at acenter part of said recessed part of said anchor, wherein a springbracket seat for holding an end of a spring that exerts a biasing forceon said plunger for movement thereof toward said valve seat is formed onsaid plunger, wherein said anchor and said plunger are operativelyassociated so that said anchor and said plunger are moved in conjunctionwith each other when said anchor is attracted to said stationary core,and wherein the sum total of the cross-sectional areas of said pluralityof through holes is larger than the minimum cross-sectional area of afuel path formed between the outer circumference of said spring bracketseat formed on said plunger and the inner circumference of saidstationary core.